Centrifugal pipe mold



lateiitecl Feb. u, 1930 Uurrao STATES PATENT OFFICE JOHN H. UHRIG, OFBEVERLY, NEW JERSEY, ASSIGNOR T0 UNI'IEI) STATES C AS'I IRON IPIIE -&IEOUNDRY GOMIANY, OF BURLINGTON, NEW JERSEY, A CORPORATION OF NEW JERSEYGENTBIFUGAL IPIIEE HOLD Application filed June 8 1927. Seria1' N0.197,273.

endecl by the deVelopment of deep cracks on their inner surfaces,generally ab the end 0f the mold into which the molten iron 1s firstintroduced, which in the case of hell ended .pipe is the hell end of themolcl, which hell end is for other reasons exposed to greater strainsthan the cylindrical portion of the mold.

I have found by examination of large numbers of used molds thatcircumferential ancl longitudinal hair line cracks on the inner Polishedsurface of the steel molcls develop early in their use atnd that wherethese surface cracks are symmetrically and comparatively closelydeveloped so a's to break the.

lnner surface intoSmall rectangles and give it a somewhat alligatorskin-like appearance, the molcl Will usually have a longer useful lifeand injurious cracks Will be slower to appear.

The object of iny invention is to provide a mold in which thedevelopment 0f symmetrical hair line cracks Will be promoted und inWhich also the smooth surface of the 1nolcl, 01' 0f such zones of themold as are most likely to fail in use, Will be microscopicallyroughened without impairing to sight o1 touch the smooth surface anclthus, as I believe, providing for a lese intimate con tact of the moltenmetal with the mold surface ancl slightly slowing the transrnission ofheat from the molten metal to the body of the mold.

- sults can how'ever be obtained by the use of the ordinary sand blast01' by etching the smooth surface to produce a. microscopio rougheningthough such tfeatments (10 not ha.rclen the roughened surfaces.

My invention consists in the provision of a smooth steel mold having itssxnooth' surface microscopically roughened and preferably .hardened inzones w'here injurious cracks are liable to occur.

In the drawings:

Figure 1 is a sectional view of a hell endecl steel mold showing itsinner polishecl surface brokenup into rectangles by fine hair line cracks wl1ich clevelop in use, and

F1gure 2 is a -rough indication of a portion of the mold surfaceenormously magnified to shoW the hardened and microscopically rouglaenedpolished surface.

A 1s the mold; A its hell end;A its smooth 1nner surface; B and C thecircumferential and longitudinal hair line surface craoks Which developin the use of the best molds. E, Fig. 2, indicates the hardenecl sk1n of the polished surface and F indicates the m1croscopic roughening of thesurface.

It Will be understood that my molcls areprepa red in the usual way andtreated after fin1sh1ng 130 microscopically roughen or harden androughen the highly finished surface 1Il zones where destructive cracksa1e most li kely t'o occur in use.

Hav1ng now des cribed my invention, what I clannas new and desire t-osecure by Letters Patent is: 1. A steel mold for the ce1it'rifugal cast-1ng of Gast iron pipes havingits inrier sur- -face highly finishecl andin partqs microscopically roughened after polishing.

2. A steel mold for the centrifugal cast- 1ng of cast iron pipes havingits inner surface h1ghly finished ancl in parts surface hardened andmicroscopically roughened after finishing. JOHN H. UHRIG.

